Taking Benadryl With Tegretol

In our latest question and answer, the pharmacist discusses whether or not Benadryl (diphenhydramine) can be used with Tegretol (carbamazepine).

Mar 25, 2018

Meg asked

Can I safely take my seizure medication, Carbamazepine 300mg at night and 75 mg of Benadryl (capsules) to help me all asleep and stay asleep? I have a very stressful job and often can't get the needed sleep. I weigh 125 lbs and am 5'3 tall. I have epilepsy from being diagnosed w/a benign brain tumor 9 yrs. ago. My seizure med is taken 300 mg twice daily.P.S. I tried 50mg. of Benadryl but it didn't help put me to sleep. Can I go up to 75 or 100mg safely?


There is no drug interaction between Benadryl (diphenhydramine) and Tegretol (carbamazepine). They are considered safe to take together.

However, it is not recommended to take more than 50 mg of Benadryl per dose for the treatment of insomnia. High doses of Benadryl are sometimes associated with paradoxical CNS (central nervous system) stimulation reactions, although this is more common in children.

Paradoxical Benadryl stimulation can result in the following symptoms:

  • Agitation
  • Insomnia
  • Muscle spasms
  • Seizures

Overdosing with Benadryl is also associated with seizures. As you have been diagnosed with epilepsy, high doses (> 50 mg per dose) of Benadryl should be avoided unless otherwise instructed by your doctor.

If the Benadryl hasn't been working for treating your symptoms of insomnia, speak with your doctor regarding safe alternatives.

Benadryl (Diphenhydramine) Information

Benadryl (diphenhydramine) is a first generation antihistamine, which often cause significant sedation.

In addition to its use for treating seasonal allergy symptoms such as a runny nose, Benadryl is also effective for treating symptoms of nausea, vomiting, and vertigo associated with motion sickness.

As Benadryl has fairly significant sedating effects, it is often used as a night time sleep aide in doses of 25-50 mg and is common component of over the counter sleep products such as ZzzQuil.

Benadryl begins to work about 20 to 30 minutes after taking by mouth and maximum blood concentrations are reached after 1 to 2 hours. The duration of action varies by individual but generally lasts 4 to 6 hours. Benadryl is generally well tolerated but can cause sedation, dizziness and respiratory depression (at high doses). 

As discussed above, high doses of Benadryl and sometimes associated with CNS excitation/stimulation.

Tegretol (Carbamazepine ) Information

Tegretol (carbamazepine) is an anti-epileptic medication and is also used as a mood stabilizer in bipolar depression.

Carbamazepine is well known to cause nausea and GI distress and therefore should be taken with meals to minimize these. Carbamazepine is also associated with rare, but serious side effects on various systems in the body (e.g. hematologic and cardiovascular system) and any side effects should be reported to the doctor immediately.

Lastly, has the interesting property of inducing (i.e. speeding up) its own metabolism and the metabolism of other drug and therefore has a large list of potential drug interactions. Before adding on additional medications, you should let your doctor know.

Taking Benadryl (Diphenhydramine) With Tegretol (Carbamazepine)

While there is no interaction between Benadryl and Tegretol, high doses of Benadryl should not be used. High doses are associated with an increased risk of CNS stimulation and rarely, seizures.

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